1. Field of the Invention
The present invention relates to a technique and apparatus for use in broadcast signal receivers, such as, for example, TV sets, that automatically searches and stores channels in which broadcast signals exist. Additionally, the technique and apparatus provide very high speed broadcast signal discrimination for use during channel selection and switching operations.
2. Description of the Conventional Art
FIG. 1 is a block diagram of an automatic channel storage apparatus of a conventional TV set. Referring to FIG. 1, the conventional automatic channel storage apparatus comprises a tuner 1, which selects the pertinent channel in accordance with the tuning data outputted from a microcomputer 8. Tuner 1 outputs intermediate frequency signals to an intermediate frequency processing unit 2, which processes the intermediate frequency signals of an image signal outputted from tuner 1. Intermediate frequency processing unit 2 also detects the original image signal. An image/color/deflection processing unit 3 receives the image signal outputted from intermediate frequency processing unit 2 and converts it into a form adequate for display on a CPT 4. A synchronization detection unit 5 is used to detect synchronous signals outputted from intermediate frequency processing unit 2. Microcomputer 8 outputs, sequentially, a series of tuning data to tuner 1.
In the conventional system, the automatic channel storage mode operates in the following manner. First, the key signals are inputted into a key matrix 6 to initialize an automatic channel storage mode operation. The storage mode operates to discriminate that a broadcast signal exists at the pertinent channel. Each time a synchronous signal is inputted through synchronization detection unit 5, the associated tuned data is stored, as a channel, in memory 7.
FIG. 2 is a detailed block diagram of tuner 1 and intermediate frequency signal processing unit 2. FIG. 2 represents a block diagram of tuner 1 and intermediate frequency signal processing unit 2. Tuner 1 comprise a high frequency amplifier 1a to amplify the input high frequency signals obtained from the antenna 9 input based on the pertinent channel data inputted from microcomputer 8 to a phase locked loop (PLL) unit 1b. PLL unit 1b does PLL processing, also. PLL unit 1b adjusts the oscillation frequency of a local oscillation unit 1c. A mixing unit 1d receives the output of high frequency amplifier 1a and outputs any received signals at the frequency tuned, or set, by the frequency of local oscillation unit 1c. The output of mixing unit 1d is transmitted to a surface elastic wave filter 1e to shape the intermediate frequency of the output.
The output surface elastic wave filter 1e of tuner 1 is received by intermediate frequency signal processing unit 2. Intermediate frequency signal processing unit 2 comprises an IF amplifier 2a to amplify the output of surface elastic wave filter 1e at a 1st, 2nd, and 3rd amplifiers. The amplified signal is sent to an image detector 2b to detect image signals and transmit the signals to an image amplifier 2c to amplify and output the image signals to image/color/deflection processing unit 3 and synchronization detection unit 5. The output of image detector 2b is also sent to an AGC detector 2d to detect the AGC signals from the output of image detector 2b. The output of AGC detector 2d is amplified by an IF AGC amplifier 2e which output is, in turn, inverted and amplified by an RF AGC inversion amplifier 2f. 
Tuner 1 also contains a high frequency AGC amplifier 1f which amplifies the RF AGC voltage outputted from RF AGC inversion amplifier 2f. The RF AGC voltage has had the ripple removed by Resistor R1 and Condenser C1. The RF AGC voltage ripple is removed after it is outputted from RF AGC inversion amplifier 2f. The output of high frequency AGC amplifier 1f is transmitter to high frequency amplifier 1a. Finally, the output of image detector 2b is outputted to the AFT voltage through the buffer 2g. 
FIGS. 3(a) to 3(c) are waveform diagrams of each unit of microcomputer 8 as shown in FIG. 1. FIG. 4 is a locus diagram of the automatic gain control voltage showing the tuning operation by conventional techniques. FIG. 5(a) is a flow chart showing how the automatic channel storage mode is applied to conventional TV sets. Finally, FIG. 5(b) is a flow chart showing a channel switching method of conventional TV sets.
The automatic channel storage mode and channel selection switching method of a conventional TV set is hereinafter described with reference to FIGS. 1, 5a, and 5b. When a televiewer outputs a pertinent key on the key matrix to carry out the automatic channel storage, microcomputer 8 perceives it, searches for the channels in which broadcast signals exist by increasing one by one the channel number, and stores those channel number perceived to have a broadcast signal in memory 7. In case where the televiewer desires to switch the channel in operation he outputs the channel increase and decrease key (not shown) and the next channel selected, each time by up/down, is the next pertinent channel stored in memory 7, during the automatic channel storage mode (described above), from the channel in use at present.
First, the automatic channel storage mode as shown in FIG. 5(a) is described by reference to FIG. 1 and FIG. 4. When the automatic channel storage mode is set up, microcomputer 8 first initializes the channels for tuning, step S1 of FIG. 5A, and after operating the PLL data of the pertinent channel, outputs the operated PLL data to tuner 1.
Accordingly, the first channel is selected at tuner 1, and, at that time, microcomputer 8 stands by, for the time necessary, for reading the synchronous signals, that is, for the standby time (approximately 300 ms) which is the time it for the synchronous signals to be detected through surface elastic wave filter 1e of tuner 1, image detector 2b of intermediate signal processing unit 2, and synchronization detection unit 5, step S4 of FIG. 5a. This is shown in the waveform diagrams of each unit of microcomputer 8 in FIG. 3(a) and 3(b). That is, if a channel switching signal, CD as shown in 3(a), is outputted to the tuner (if a tuning data PLL DATA of the pertinent channel is outputted to the tuner), and if there is any broadcast signal, it takes approximately 300 ms until the recognition signal ID is inputted through synchronization detection unit 5, as shown in the waveform diagram in FIG. 3(b).
After confirming whether the synchronous signals exist in the channel selected at present through path, step S5 of FIG. 5(a), if any, it is discriminated that there exist a broadcast signal in the selected channel. The data of the pertinent channel (channel number or frequency) is stored in memory 7.
In the following step, it is confirmed whether all channels have been searched, step S7 in FIG. 5a. If any channels remain to be searched, the channel number is increased by one (N+1, channel increase), step 5B of FIG. 5A, and the search is repeated until all channels have been searched. After searching all channels, the operation is ended.
Secondly, the channel selection and switching method as shown in FIG. 5(b) is described by reference to FIG. 1 and FIG. 4. When a televiewer desires to switch a channel in operation he presses the numeric key corresponding to the pertinent channel number or selects the next channel using the channel increase and decrease keys. Microcomputer 8 operates the PLL DATA of the selected channel, and outputs it to tuner 1, step S1 of FIG. 5B. Accordingly, the pertinent channel is selected at tuner 1, and at that time microcomputer 8 stands by for the time necessary for reading exactly the synchronous signals, that is, the standby time is 300 ms until the synchronous signals are detected through surface elastic wave filter 1e of tuner 1, image detector 2b of intermediate frequency signal processing unit 2, and synchronization detection unit 5, step S2 of FIG. 5B. It is then discriminated whether any synchronous signal exists, step S3 of FIG. 5B, and if any signal is discriminated, the optimum picture is received by auto fine tuning (AFT) (not shown), step S4 of FIG. 5B. This is shown in the waveform diagrams of microcomputer 8 in FIGS. 3(a, b, c). In other word, if a channel switching signal CD, as shown in FIG. 3(a) is outputted to tuner 1, and if there exists any broadcast signal, it takes about 300 ms until the recognition signal ID is inputted through synchronization detection unit 5, as shown in the waveform diagram in FIG. 3(b). If there is any synchronous signal, a waveform diagram to make the AFT adjustment is shown in FIG. 3(c). It takes approximately 500 ms until a stable picture is outputted after selecting the channel switching operation. Consequently, methods, such as turning on the picture mute or outputting a blue-back picture for the approximately 500 ms period, are employed to prevent any screen blinking during channel switching.
The output process of the high frequency automatic gain control (RF AGC) and the intermediate frequency automatic gain control (IF AGC) voltage is hereinafter described on reference to FIG. 2 and FIG. 4.
As shown in FIG. 2, the broadcast signals received through antenna (ANT) 9 are amplified to the prescribed level through high frequency amplifier 1a, and mixed with the oscillation signals of local oscillation unit 1c in mixer 1d. The surface elastic wave generated by the mixing is filtered by surface elastic wave filter 1e and supplied to intermediate frequency signal processing unit 2.
In intermediate frequency signal processing unit 2, the received intermediate frequency signals are amplified through intermediate frequency amplifier 2a and any image signals are detected through image detector 2b. The detected image signal is outputted to image/color/deflection processing unit 3 and synchronization detection unit 5 after being amplified through image amplifier 2c. The output of image detector 2b is also sent to AGC detector 2d to detect the AGC. AGC detector 2d has its output rectified by a resistor R2 and a condenser C2. The rectified output of AGC detector 2d is sent to IF AGC amplifier 2e. This IF AGC voltage outputted as a direct current (DC) value is adjusted for the gain of the 1st and 2nd amplifies of IF amplifier 2a through IF AGC amplifier 2e. The RF AGC voltage is obtained by inverting and amplifying the IF AGC voltage using RF AGC amplifier 2f. The RF AGC voltage has the ripple removed by a resistor R1 and a condenser C1. The RF AGC voltage, after the ripple is removed is sent to high frequency AGC amplifier 1f. 
The IF AGC and RF AGC voltages are described using the AGC voltage locus diagram in FIG. 4. As the AGC detector 2d signals are inputted into IF AGC amplifier 2e, it attempts to change the value of the IF AGC voltage, and when the IF AGC voltage field strength is attempted to be changed, the RF AGC voltage is changed such that the value of the IF AGC voltage remains constant, and the more the IF AGC voltage field strength is increased, the more the RF AGC voltage is deceased, and because it decreases the gain of the high frequency amplifier 1a in tuner 1, a stable picture can be guaranteed even at the time of a strong field.
In the above-mentioned conventional automatic channel storage apparatus and method, it takes about a 300 ms delay per channel for the detection of the synchronous signals through surface elastic wave filter 1e of tuner 1, image detector 2b of intermediate frequency signal processing unit 2, and synchronization detection unit 5, in order to read exactly the synchronous signals, which is the grounds used to discriminate that the broadcast signal exists in the channel at the time of automatic channel storage. In case of the PAL B/G mode in Europe areas, it requires about 2 to 5 minutes for scanning 115 channels. The NTSCM mode of 180 channels requires about the same amount of time. This is disadvantageous because televiewers become bored.
Moreover, the conventional channel selection switching apparatus and method takes about 500 ms to output a stable picture after selecting the channel by the channel switching operation. Therefore, it is required to consider a supplementary means, such as turning on the picture mute or outputting a blue-back picture for the said period, to prevent a screen blinking during channel switching.
An object of the present invention is to provide an apparatus and method for performing a discrimination on whether there exists any broadcast signal in a pertinent channel by using the automatic gain control signal, for example the IF AGC signals, as signals identifying the broadcast signals.
Another object of the present invention is to provide an apparatus and method for performing the automatic channel storage at high speed, by using the automatic gain control signals as identification signals, reducing the AGC output time using speed-up drive units for the AGC signals, and thereby reducing the time for discriminating whether there exist any broadcast signals in the pertinent channel.
The further object of the present invention is to provide the apparatus and method to perform the channel switching operation at high speed, by reducing the time taken until the channel selected at the time of channel selection switching, using the speed-up drive unit of the said automatic gain control signals.
The very high speed broadcast signal discrimination apparatus achieving the objects according to the present invention comprises a tuning means to select a pertinent channel in accordance with tuning data and a broadcast discrimination means which discriminates whether a broadcast signal exists on the pertinent channel based on an AGC signal.
A further very high speed broadcast signal discrimination apparatus achieving the objects according to the present invention comprises a tuning means to select a pertinent channel in accordance with tuning data, and to output intermediate frequency signals; an intermediate frequency processing means to process the intermediate frequency signals of an image signal outputted from the tuner, to detect and output the image signals, and then to output automatic gain control signals and a broadcast signal discrimination means to receive AGC signals from the intermediate frequency processing means and to discriminate, on the basis of those signals, whether there exists any broadcast signal.
The very high speed automatic channel storage apparatus, which is another object of the present invention, comprises a tuning means for selecting a pertinent channel in accordance with tuning data and a broadcast discrimination means which discriminates whether a broadcast signal exists on the pertinent channel based on an AGC signal. If it is discriminated that a broadcast signal exists on the pertinent channel, then the pertinent channel information is stored in a channel storing means.
A further very high speed automatic channel storage apparatus which is another object of the present invention comprises a tuning means to select a pertinent channel in accordance with tuning data, and to output intermediate frequency signals; an intermediate frequency processing means to process the intermediate frequency signals of an image signal outputted from the tuner, to detect and output the image signals, and then to output AGC signals; a speed-up drive means to control the speed of the output of the AGC signals; a broadcast signal discrimination means to receive the AGC signals from the intermediate frequency processing means, and to discriminate on the basis of those signals, whether there exists any broadcast signal; and a channel information storage means to store the pertinent channel that have broadcast signals.
The very high speed channel switching apparatus which is a further object of the present invention comprises a tuning means to select a pertinent channel in accordance with tuning data, and to output intermediate frequency signals; an intermediate frequency processing means to process intermediate frequency signals of an image signal outputted from the tuner, to detect and output the image signals, and then to output AGC signals; a speed-up drive means to control the speed of the output of the AGC signals; a synchronization detection means to detect synchronous signals from the image signals outputted from the intermediate frequency signal processing unit; and a channel switching control means to output the tuning data by the tuning means upon a command to switch the channel, to receive the input of the synchronous signals of the synchronization detection means, after driving the speed-up drive unit, and to turn off the speed-up drive units after completing the channel switching operation by carrying out an AFT adjustment.
According to the present invention, as embodied herein, the technique and apparatus carry out, at high speed, the broadcast signal discrimination by discriminating on the basis of the automatic gain control (AGC) signals that a broadcast signal exists in a channel. The system also provides a very high speed channel storage apparatus and method of television designed to discriminate on the basis of the AGC signals whether there exist any broadcast signals, and to search and store the channels, at very high speed, using speed-up drive units. Finally, the techniques and apparatus provide very high speed channel selection and switching using speed-up drive units.
Additional objects, embodiments, and advantages of the invention are set forth in part in the description which follows, and impart will be obvious from the description, or may be learned by practice of the invention. The objects, embodiments, and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.